In recent years, the frequency band that an antenna needs to cover has expanded as a result of faster, higher-capacity radio communication, in particular on mobile terminals and the like. Therefore, in order to implement an antenna that supports numerous frequency bands, a tunable antenna that can switch the resonance frequency has been developed by providing electronic components, such as switches and tunable capacitors, inside a matching circuit connected between the antenna element and the feed.
Tunable antennas that vary the actual antenna element length by providing electronic components such as switches and tunable capacitors in the antenna element have also been proposed. With such a tunable antenna, by changing the reactance component of the antenna element, the resonance frequency can be switched dynamically as compared to a structure in which electronic components are disposed inside the matching circuit.